The avian core will have two classes of aims. It will supply enough young, middle-aged, and old parakeets and/or tissues to service the needs of Projects 1, 2, and 3 and it will also begin characterizing actuarial and reproductive aging in clean colonies of parakeets kept under uniform conditions. In addition, this core will begin characterizing anatomic and clinical pathology as well as microbiological status in this species and it will provide birds and/or tissues to unaffiliated investigators who would like to have them. The parakeet colony will be maintained in pseudo-SPF conditions with only sterilized food, water, bedding, nest boxes, and perches entering the facility and surgical scrub-in for any personnel entering. In addition, regular health surveillance will be performed via randomized monitoring of blood and fecal samples plus complete necropsy and microbiological assessment of sentinel birds. In the room used for demographic characterization, only birds bred in this facility will be introduced. In another room, middle-aged and older birds purchased from other sources will be housed. All these individuals will be quarantined for at least 60 days and serologically tested for common psittacine infectious diseases before leaving quarantine and entering the facility, Complete demographic and health records will be maintained on all birds.